东昆仑五龙沟地区猴头沟二长花岗岩年龄、成因、源区及其构造意义

发布时间：2018-02-03 03:07

本文关键词： 猴头沟二长花岗岩岩石地球化学锆石U-Pb定年 Hf同位素东昆仑　出处：《吉林大学学报(地球科学版)》2016年02期 　论文类型：期刊论文

【摘要】：对东昆仑造山带五龙沟地区的猴头沟二长花岗岩开展了详细的岩相学、地球化学、锆石U-Pb年龄及Hf同位素的分析测试和研究工作。LA-ICP-MS锆石U-Pb测年表明,猴头沟二长花岗岩的206Pb/238U加权平均年龄值为(419.0±1.9)Ma,属于晚志留世。岩石地球化学数据表明:猴头沟二长花岗岩属于高钾钙碱性系列的A2型花岗岩,富SiO_2、K_2O、Y(33×10-6)和Yb,贫Al_2O_3和Sr(100×10-6),具有强烈的负铕异常;Rb、Th、U、La、Ce、Nd相对富集,Nb、Ta、Ba、Sr、P、Ti亏损。锆石的Hf同位素研究表明,其εHf(t)值为0.2~5.1,对应二阶段模式年龄(TDM2)为1 066~1 371 Ma,由此推测花岗岩源区来自中元古代镁铁质下地壳部分熔融。微量元素及其特征比值的构造判别图解表明,猴头沟二长花岗岩形成于早古生代晚志留世东昆仑造山旋回的造山后伸展阶段。据此认为,原特提斯洋在东昆仑地区的最晚闭合时限应该不晚于晚志留世末期(~419 Ma),而不是前人认为的早泥盆世。
[Abstract]:Detailed lithofacies and geochemistry have been carried out on the Erzhang granite in the Wulonggou area of the East Kunlun orogenic belt. Zircon U-Pb dating and HF isotopic dating. The weighted average age of 206Pb / 238U of Ertougou monzogranite is 419.0 卤1.9 Ma. It belongs to the late Silurian. The petrogeochemical data show that the Erfeldite belongs to the A2-type granite of high potassium calc-alkaline series, rich in SiO2K _ 2O _ 2 _ T _ (33 脳 10 ~ (-6)) and Yb. Poor in Al_2O_3 and Sr(100 脳 10-6, with strong negative europium anomaly; The relative enrichment of ND in RbBX, Th, T, Ba, O, Sr, PU, Ti is depleted. The HF isotopic study of zircon shows that the 蔚 Hftof the zircon is 0.2 ~ 5.1. The corresponding two-stage model age (TDM2) is 1 066 / 1 371 Ma. The source region of the granite is derived from the partial melting of the lower crust of the Mesoproterozoic magnesite. The tectonic discriminant diagrams of trace elements and their characteristic ratios show that. The Ernanite formed in the post-orogenic extension stage of the late Silurian East Kunlun orogenic cycle in the early Paleozoic. The last time limit for the closure of the original Tethys in the East Kunlun region should be no later than the late Silurian period of 419 Ma, rather than the early Devonian thought by previous generations.
【作者单位】：吉林大学地球科学学院;吉林大学学报编辑部;
【基金】：中央高校基本科研业务费专项资金(JCKY-QKJC34) 国家自然科学基金项目(41572056)~~
【分类号】：P588.121
【正文快照】： 0引言五龙沟地区位于青海省都兰县境内,大地构造位置处于东昆仑造山带中东段。东昆仑造山带内出露大量早古生代和晚古生代—早中生代两个时期的侵入岩,分别是原特提斯和古特提斯两期构造演化的产物[1]。因此,对这两套不同时期侵入岩开展细致的研究,能够为反演东昆仑造山带原特

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